本論文的主題是以四波混頻(Four-wave mixing)為主要物理機制在單光子等級實現高效率之光波長轉換，而目前我們的實驗系統在古典光條件下以及單光子等級(single photon level)條件下皆可達75%之光波長轉換效率。
在一開始會先闡述本論文之研究目的以及其未來在量子資訊科學的重要性，接著會先介紹一些關於本研究的重要基礎原理：電磁波引發透明機制(Electromagnetically Induced Transparency Mechanism)，以Λ-type電磁引發透明(EIT)圖像為主軸，實際數學推導其物理參數之關係式。然後再更進一步地討論Double Λ-type EIT系統，意即本論文中所使用的四波混頻(Four-wave mixing)之物理圖像。
在正式四波混頻光波長轉換實驗之前，會先簡介本實驗捕捉銣((_ ^87)Rb)原子團的架設以及在做四波混頻時會使用上的各種光路，如：探測光(Probe)、波長為780nm之耦合光(Coupling)、波長為795nm之耦合光(Driving)和黎曼幫浦(Zeeman pumping)以及各個實驗光在四波混頻實驗時所設定之時序。
而對於Zeeman pumping的優化也是四波混頻實驗前重要的步驟之一，因為在作Four-wave mixing時，須有效地將對於我們所使用的Double Λ-type EIT圖像中所不需要的能態上之原子數清空，並把原子準備在實驗所需的能態，避免造成轉換效率降低。接著則是先以理論模擬決定系統對於四波混頻轉換效率最佳之參數，如：Coupling光與driving光之拉比頻率(Rabi frequency)值等，再討論探測光之高斯光束參數對於轉換效率的影響及耦合光均勻度之影響。
而在前面的部分皆是以古典光作四波混頻光波長轉換之實驗，接下來我們將把在古典光的轉換效率成果運用在單光子等級，此外也對古典光衰減至單光子等級下的特性以及經分光後兩道光的關聯性作討論，並在最後呈現在單光子等級下的四波混頻波長轉換效率之結果。

The thesis’ topic is about realizing the high-efficiency wavelength conversion based on four-wave mixing mechanism with single photon level. In our experiment system, the wavelength conversion efficiency is about 75%.
In Chapter 1, I will introduce the motivation of wavelength conversion with single photon level and explain its importance in quantum information technology in the future. In Chapter 2, I will talk about the basic principle “Electromagnetically induced Transparency(EIT)” which is the most important physics mechanism in our research. Based on Λ-type EIT, I will go further to introduce the four-wave mixing which is double Λ-type EIT. Finally, I will do some theoretical calculation by Maxwell-Schrödinger equation and optical Bloch equaiton. In Chapter 3, I will show our experiments setup and introduce each laser’s function and time rail.
In Chapter 4, we mainly discuss the optimization of Zeeman pumping. Because we need to pump the atom population from unwanted energy states to energy states which is used to do the four-wave mixing experiment. In Chapter 5, I will do some simulation to predict the best physics parameters in our system and compare the theoretical prediction and experiment results. Then we start to discuss how to optimize the wavelength conversion efficiency. Finally, I will show the experiment result of coherent wavelength conversion with single photon level and their properties in Chapter 6.
The Chapter 7 is the test result of experiment equipment in our system.

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